The four fundamental ecological processes of ecosystems are the water cycle, biogeochemical (or nutrient) cycling, energy flow and community dynamics, i.e. how the composition and structure of an ecosystem changes following a disturbance (succession).
Water cycle.Water (H20) is the most abundant molecule on Earth. It is the only one that can be found naturally in solid, liquid and gas and is essential to all life on Earth. From the ability to store energy through photosynthesis to the consumption of energy through respiration, the properties of water provide a perfect medium for biological reactions that occur within cells.
The water that evaporates from the ocean with the sun's energy is transported by the circulation of winds around the planet. Upon rising over the contours of the mountains, it cools and becomes rain, providing moisture to rain forests, jungles, grasslands and scrub. It feeds streams, rivers, lakes, and groundwater before eventually returning to the sea. On this long journey, it is absorbed by plants and drunk by animals, which all require water as it constitutes between 55 - 80% of all living things.